Research On Deformation And Vibration Measurement Method Of Machining Process Of Curved Thin-walled Parts

Curved thin-walled parts are widely used in aerospace,automobile manufacturing,military industry and other fields because of their unique characteristics of light weight,high strength,and high load-bearing capacity.Thin-walled parts are prone to cutting deformation and machining vibration during milling processing due to their low rigidity,which seriously affects the dimensional accuracy and surface quality of thin-walled parts.The dynamic characteristics of curved thin-walled parts at different cutting points are different,and the first several modes will have different degrees of influence on it.In the cutting process,it is necessary to consider the combined effect of the previous multi-modes.In addition,the real-time online measurement of vibration and deformation during the processing of curved thin-walled parts still lacks effective methods.Therefore,it is of great practical significance to deeply study the dynamic characteristics of thin-walled parts in the process of processing,and to propose reasonable and effective manufacturing processes and vibration deformation measurement methods.In view of the above problems,this article firstly studies the dynamic characteristics of thin-walled parts based on the finite element method.Secondly,a prediction model for the dynamic characteristics of thin-walled parts based on path changes is established.Thirdly,an experimental research on the milling process of thin-walled parts is carried out.Finally,a real-time online measurement method for the deformation of curved thin-walled parts is proposed.The main research contents and conclusions are as follows:1)Based on the finite element method,research on the dynamic characteristics of flat and curved thin-walled parts is carried out.The effects of different heights and thicknesses on the natural frequency and mode shape of thin-walled parts are studied.The results show that the natural frequency increases with the increase of the thickness of the thin-walled part,and decreases with the increase of the height,and the influence of the height on the natural frequency is greater than the influence of the thickness.In the subsequent cutting of thin-walled parts,the influence of natural frequency should be avoided,and pave the way for the follow-up work of the thesis.2)A prediction model of the dynamic characteristics of thin-walled parts based on path changes is established.Based on the single-point excitation single-point response dynamic test impact test,the influence of the path change of the thin-walled parts on the modal parameters such as the frequency,damping,and residue of the workpiece is studied.Research shows that the closer the test point of the thin-walled part is to the measured part,the higher the natural frequency and the smaller the deformation,and the frequency changes at both ends of the part are basically symmetrical;based on the first two modes,the dynamic characteristics of the cutting points on the cutting path of thin-walled parts can be better evaluated;Based on the modal parameters obtained from the hammering and the cubic polynomial fitting,a predictive model was constructed to realize the modal parameters of the thin-walled parts at any point in the machining process.Finally,the experiment verifies the effectiveness of the prediction model.3)Experiments on the milling process of thin-walled parts were carried out.Considering the influence of feed speed and spindle speed on the cutting force and cutting vibration of flat and curved thin-walled parts,the results show that with the increase of spindle speed and feed speed,the cutting force and cutting vibration of the thin-walled parts on the plane decrease,and the cutting force and vibration of the thin-walled parts on the curved surface increase;the influence of spindle speed on the cutting force of thin-walled workpieces is greater than the influence of feed speed;the cutting vibration amplitude of thin-walled parts shows a trend of "big at both ends and small in the middle",and the change of the cutting vibration amplitude of the flat thin-walled parts is greater than that of the curved thin-walled parts.4)A real-time online measurement method for machining deformation of curved thin-walled parts is proposed.This method overcomes the problems of time-varying cutting point,timevarying curvature,sensor tracking displacement and time-varying rotation angle of the curve trajectory during processing.Mainly involved: establish a laser sensor measurement trajectory model through tool processing trajectory;based on Lab VIEW software,a motion device system was built and a real-time online measurement system program was written;the real-time online measurement experiment of processing deformation of thin-walled parts is carried out to verify the effectiveness of the method.